public void FunctionTest()
{
double sigma = 2.1;
Laplacian target = new Laplacian(sigma);
double[] x = { 1, 3 };
double[] y = { -1, 2 };
double expected = 0.34479878120059682;
double actual = target.Function(x, y);
Assert.AreEqual(expected, actual);
// For the same input, product should be 1
Assert.AreEqual(1.0, target.Function(x, x));
}